Definitions

penstemon davidsonii

Penstemon

[pen-stee-muhn, pen-stuh-muhn]

Penstemon (Beard-tongue) is a large genus of North American and East Asian plants traditionally placed in the Scrophulariaceae family. Due to new genetic research it has now been placed in the vastly expanded family Plantaginaceae.

They have opposite leaves, partly tube-shaped and two-lipped flowers and seed capsules. The most distinctive feature of the genus is the prominent staminode, an infertile stamen. The staminode takes a variety of forms in the different species; while typically a long straight filament extending to the mouth of the corolla, some are longer and extremely hairy, giving the general appearance of an open mouth with a fuzzy tongue protruding and inspiring the common name beardtongue.

Most penstemons are herbaceous perennials, the remainder being shrubs or subshrubs. Heights can range from 10 cm to as much as 3 meters.

The one Asiatic species previously treated in Penstemon is now placed in a separate genus Pennellianthus. This leaves Penstemon a mostly nearctic genus, with a few neotropical species. Although widespread across North America, and found in habitats ranging from open desert to moist forests, and up to the alpine zone, they are not typically common within their range.

History

Native Americans long used penstemon roots to relieve toothache. John Mitchell published the first scientific description in 1748; although he only named it as Penstemon, we can identify it as P. laevigatus. Linnaeus then included it in his 1753 publication, as Chelone pentstemon, altering the spelling to better correspond to the notion that the name referred to the unusual fifth stamen (Greek "penta-", five). Mitchell's work was reprinted in 1769, continuing with his original spelling, and this was ultimately accepted as the official form, although Pentstemon continued in use into the 20th century.

Although several more species were found in the 18th century, they continued to be classified in Chelone until about the 1820s. The period of 1810 to 1850 increased the number of known species from 4 to 63, as expeditions travelled through Mexico and the western United States, followed by another 100 up to 1900.

During this time, seeds began to be offered for sale in Europe, the earliest known dating from 1813, with John Fraser offering four species in London, followed by Flanagan & Nutting offering nine species in their 1835 catalog. Subsequently many hybrids were developed in Europe.

Fieldwork in the remote parts of the Great Basin during the 20th century brought the total number of species known to over 250. The genus was extensively revised by David Keck between 1932 and 1957; in 1946 the American Penstemon Society was formed to promote both horticultural and botanical interest.

Horticulture

Although penstemons are among the most attractive native flowers of North America, Europe has always been far more active in their cultivation, and hundreds of hybrids have been developed there since the early 1800s. The earliest development is somewhat shrouded in mystery; for instance Flanagan & Nutting's 1835 catalog mentions a 'Penstemon Hybridum' but does not describe it.

By 1860, a half-dozen French growers are known to have developed hybrids, most notably Victor Lemoine, while in 1857 the German Wilhelm Pfitzer listed 24 varieties. In 1861 the Royal Horticultural Society held trials in which 78 varieties were entered. The Scottish firm of John Forbes first offered penstemons in 1870, eventually becoming the biggest grower in the world; in 1884 their catalog listed 180 varieties. By 1900 Forbes had offered 550 varieties, while Lemoine had developed nearly 470 by the time of his death in 1911. Few of these have survived to the present day.

A number of different species have been used in the hybridization process, notably P. cobaeus and P. hartwegii.

In North America, penstemon species are often used in Xeriscape landscaping, as many are native to desert or alpine regions and thus quite hardy. One of the largest collections of penstemon species in North America is found at The Arboretum at Flagstaff, which hosts a Penstemon Festival each summer.

Species

References

  • David Way & Peter James, The Gardener's Guide to Growing Penstemons (David & Charles Publishers, 1998) ISBN 0-7153-0550-6

External links

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